In some CATV electronic signal filter applications, magnetic isolation shielding is required between filter sections within a filter cavity of the filter housing in order for the filter to function properly. Isolation shields are typically positioned to extend above and/or below the surface of a circuit board on which discrete electronic components comprising the filter sections are positioned. This is shown, for example, in U.S. patent application Ser. No. 10/301,014 (now U.S. Pat. No. 6,759,927), which is owned by the assignee of the present invention and the entirety of which is incorporated herein by reference. Although the '014 application provides magnetic isolation shields that can be assembled to a circuit board using automated Z-axis manufacturing techniques, it is still necessary to connect the shield to the circuit board and the filter housing to achieve grounding contact therebetween after the circuit board and shield sub-assembly is inserted into the filter housing.
That is, in order to provide the required grounding contact between the circuit board, the magnetic isolations shields, and the housing, it is necessary to solder the shields to the circuit board and the filter housing during assembly of the filter. The post-insertion soldering step involved with connecting the shields to the filter housing, however, increases the manufacturing costs of the electronic signal filter. Moreover, achieving the required ground connection in this manner can be quite difficult, since the shields are positioned inside the filter housing before being soldered.
Since such manual soldering steps are costly, with respect to both manufacturing speed and expense, it would be desirable to provide an electronic signal filter that includes magnetic isolation shields that do not require an additional manual soldering step to provide a secure grounding connection between the shield members and the filter housing.
Protection from excessive current surges through CATV filters is also an important consideration. As described in U.S. Pat. No. 6,560,087, which is owned by the assignee of the present invention and the entirety of which is incorporated herein by reference, a spark gap can be provided by properly spacing a portion of a magnetic isolation shield from a plated via or conductive trace formed on a surface of a circuit board. The spark gap effectively shunts the excess current to ground and protects downstream electronic components from the otherwise harmful current surge.
In the devices of the '087 patent, however, the magnetic isolation shield into which the spark gap is incorporated must also be connected to ground in order to properly perform the desired current shunting function. That is, the shield must be soldered to the filter housing to provide the required ground connection. Again, this requires a manual soldering step performed after the circuit board has been inserted into the filter cavity within the filter housing.
Thus, it would be desirable to provide an electronic signal filter having a component that provides the desired surge protection without requiring additional manual post-insertion soldering steps in order to provide grounding contact.
U.S. Pat. No. 6,429,754, and U.S. patent application Ser. No. 10/187,455 (now U.S. Pat. Nos. 6,674,342 and Ser. No. 10/329,055 (now U.S. Publication No. 2003-0151470), which are owned by the assignee of the present invention and the entireties of which are incorporated herein by reference, disclose ground post members that facilitate automated Z-axis manufacturing and solderless ground connections between opposed filter housing members of a split housing filter and a circuit board interposed therebetween within the filter cavity. While the ground posts of the '754 patent, the '455 application and '055 application afford solderless ground connections and eliminate some soldering steps in general, the use of such ground posts is not applicable in many filter applications, such as those that employ compact filter housings that are not split along the longitudinal axes. Thus, room for improvement remains.
Another drawback associated with conventional electronic signal filters is that multiple components are generally required in order to provide multiple features such as shielding, surge protection, and grounding. Using multiple individual precision components also drives up the production cost of the final product, due to the number of manufacturing sub-assembly steps required and complex manual soldering steps that must be performed after the sub-assemblies are positioned in the filter housings.
Accordingly, it would be desirable to provide an electronic signal filter whose component parts can be assembled into an electronic signal filter final product without any soldering steps performed after the circuit board is inserted into the filter housing. It would also be desirable to provide an electronic signal filter whose overall number of discrete sub-assembly components could be reduced. It would also be desirable to provide an electronic signal filter electronic signal filter including a single component that provides ground contact between the circuit board and the filter housing, that provides magnetic isolation shielding and that provides surge protection, all without any post-insertion soldering steps.